“We don’t let it directly determine what we publish, but the fact is, with every book, there is always fear that the book is going to be pulled. The authors feel very vulnerable,” said David Bernstein, publisher of Bombardier Books, a conservative imprint of Post Hill Press. Conservative fears were realized this month when the book “When Harry Became Sally: Responding to the Transgender Moment,” by Catholic scholar Ryan T. Anderson, vanished from the Amazon website three years after it was published. Four Republican senators, including Utah’s Mike Lee, called the action “political censorship,” saying in a letter to CEO Jeff Bezos that “Amazon has openly signaled to conservative Americans that their views are not welcome on its platforms.”